Light which strikes the eyes of the individual is gathered by the retina and is converted into signals for transmittal to the brain. The brain processes those sensory signals to guide the thought and action of the individual. Thus, the perception of reality is a complicated combination of visual experiences and the neural structure of the brain.
Visual perception is the process of interpreting the surrounding environment with the eyes. The individual does not directly sense the surrounding environment, but only the reflective and ambient light which is present. The individual's knowledge of space, surface texture and movement is simply the most plausible interpretation of the complex patterns of light captured by the eyes.
The world which surrounds humanity is constantly in motion. An individual will move through the world while at the same time the world moves around the individual. The correct interpretation of the visual motion is critical to a virtual infinity of visually related tasks. Simple examples of everyday tasks requiring the accurate interpretation of visual information include driving a car, walking through a park, watching a movie or even reading a book. In addition, accurate interpretation of motion information is critical for optimum performance in athletic endeavors such as baseball, football, hockey, basketball, tennis, handball or soccer.
With regard to motion, the true velocity of an object is defined as the distance traveled by the object divided by the time it takes the object to move that distance. Surprisingly, the perception of that motion is not solely related to this true velocity of the moving object.
Perceived motion does not depend only on time and distance. When the luminance (brightness) of the light reflected from a moving object is matched to the luminance of the background, movement of the object will appear to slow down. This balanced state is called equiluminance. At equiluminance, all the information about the object and the background is carried by color differences.
The perceived slowing is due to the manner in which the brain processes information. At present, the exact physiological connections which make up motion perception are not precisely known. It is known that this phenomenon indicates the presence of multiple pathways or channels of motion information processing in the brain and that these channels seem to extract information from specific properties in the stimulus.
Perception begins with light impinging upon the rods and cones of the retina. Rods sense information under very low illumination levels. In normal daylight vision they are saturated and thus play no role in the phenomenon of equiluminance. The cones are separated into three types: red, green and blue. The cones on the retinas respond to a broad spectrum of light. Red cones are most sensitive to light in the red part of the visible spectrum. Green cones are most sensitive to light in the green part of the visible spectrum. Blue cones are most sensitive to light in the blue part of the visible spectrum.
The signals from the cones are roughly combined into three pathways as illustrated in FIG. 1 which are used to transmit the information to the brain. The first is an achromatic (or luminance) pathway which is formed by summing the signals generated by the red and green cones at a given location. The luminance pathway corresponds to the brightness or intensity of the impinging light.
The remaining two pathways are the red/green and the blue/yellow chromatic pathways. The red/green pathway is composed of the difference between the signals generated by the red and green cones at the given location. The blue/yellow pathway is composed of the difference between the summation of the red and green cone signals, namely, the luminance pathway, and signals generated by the blue cones at the given location.
For an average individual under normal lighting conditions, motion perception is dominated by the luminance pathway. Motion sensed along the chromatic pathways influences the overall perceived motion to a lesser extent. Under equiluminant conditions, no motion information is carried by the luminance pathway, isolating the chromatic pathways. When this happens, the motion perceived by the individual is slower than the perceived motion of an object with luminance information.
It is presently believed that the perceived motion of a pattern is comprised of information received from all three of the described pathways. The experimental evidence suggests that each person balances the input from each of the three pathways in a different manner. For example, the same moving pattern may produce different perceived velocities in different subjects depending on the particular combination of luminance and chrominance in the stimulus.
Accordingly, what is needed is a method of testing the motion perception signals from each pathway for a given individual. The method should also be able to provide an overall measurement of motion perception to allow diagnosis of special abilities or disabilities as compared to the general population. The method further should suggest measures to either enhance normal motion perception ability or improve the motion perception of disabled subjects.
The present invention meets those needs.